Millions of consumers who buy calcium-fortified products to get more calcium into their diets may be in for a surprise.

According to research conducted by Robert P. Heaney, M.D., professor of medicine at Creighton University Medical Center, calcium-fortified products, typically orange juice, differ substantially in the way the calcium is absorbed by the body.

According to Heaney's research, published in the Journal of the American Dietetic Association, the addition of calcium to a product does not guarantee that the consumer is getting the full benefit of what is on the label. It depends on the absorbability of the added calcium.

Previous research by Heaney, holder of the John A. Creighton University Professorship, showed that the calcium added to some orange juices has features suggesting poor absorbability. Heaney's article confirms that suggestion between two national brands of orange juice.

The Food and Drug Administration's fortification policy states that a nutrient added to a food is appropriate only when the nutrient is physiologically available from the food. According to Heaney, few manufacturers optimize the availability of calcium they add to their products.

"Since consumers presume, based on the label, that they are getting calcium by consuming the product, nutrition professionals should strongly encourage manufacturers to provide information about the bioavailability of not only calcium but of the many other nutrients added to foods," said Heaney. "There is a need both for better fortification systems matched to the food being fortified and for better quality assurance with respect to selected fortification methods.”.